It has been disclosed in the past, at least to a limited extent, that in certain surgical procedures conducted within a body cavity, such as, for example, a phacoemulsification procedure, a lens capsule, located in an anterior chamber of a human eye, is broken into particles and residual debris (all hereinafter referred to as “the particles”), must be continuously withdrawn or flushed from the site of the surgery. During the surgical procedure, an irrigation fluid is fed, for example, by gravity or positive pumping, into the cavity, and the irrigation fluid and the broken lens particles contained therein are withdrawn, as an aspiration fluid, from the cavity by a pumping action, which develops an aspiration fluid flow and a negative or vacuum pressure. Thereafter, the particles are segregated from the aspiration fluid, by filtering, and the particle-free filtered fluid is then transferred to a waste depository, or fluid-collection chamber, at a site remote from the site of the surgery.
When performing a phacoemulsification procedure, it is essential to maintain a positive pressure within the anterior chamber of the eye, which contains the lens capsule. A negative pressure within the chamber may cause the cornea to collapse. In order to maintain a positive pressure within the anterior chamber, the flow of the irrigation fluid is maintained at a rate which is at least slightly greater than the flow rate of the aspiration fluid.
The following example of a surgical apparatus, which includes an aspiration system, is used in a phacoemulsification procedure regarding the removal of cataract tissue and the affected lens of the eye, in the form of the particles. The principle of operation of the below-described phacoemulsification surgical apparatus could be used in other surgical procedures, such as, for example, knee and shoulder surgery, where removal of particles from the surgical site is critical
Apparatus used in previous phacoemulsification surgical procedures include a hand piece, which is held and manipulated by a surgeon during the procedure. The hand piece supports a hollow ultrasonically-driven cannula having an open free-end tip at an inlet end of the hollow cannula. The surgeon maneuvers the hand piece to insert the cannula tip through an incision in the patient's cornea and into the patient's eye. The cannula tip is then moved by the surgeon adjacent and/or into engagement with a cataractous lens of the eye to break the lens into the particles.
As the lens is broken into the particles, an irrigation fluid is fed by gravity, or pumped, into the eye, through an irrigation line, to initiate a process of flushing the particles from the eye. An aspiration system is employed to continue the flushing action of the now particle-laden fluid through and out of the eye in the form of an aspiration fluid. An aspiration line of the aspiration system provides a conduit for the aspiration fluid, and includes an inlet opening formed by the open free-end tip of the cannula, the hollow cannula, a first aspiration tube, a filter-containing housing, a second aspiration tube, and an outlet end of the line. The aspiration system further includes an aspiration pump, which facilitates the flow of the aspiration fluid from the eye in an aspiration direction, i.e., away from the eye and toward the outlet end of the aspiration line, by developing a fluid-flow stream and a relatively low vacuum pressure in the aspiration line.
The aspiration pump is typically one of three known types of fluid pumps, namely a peristaltic pump, a venturi pump, or a diaphragm pump. For purposes of explanation, the above-described apparatus uses a peristaltic pump, which includes a circular rotating pump head having a periphery adjacent, and spaced from, a circular wall of a stationary pump housing. Radially-spaced rollers are mounted on the periphery of the head for orbiting movement about an axial center of rotation of the head. An axially-stationary, flexible aspiration tubing is located about the periphery of the head, and between the head and the circular wall of the housing, for passage of fluid through the tubing. As the head is rotated, each successive orbiting roller pinches successive portions of the stationary tubing against the circular wall of the housing, thereby pushing fluid forward within the tubing, in the direction of rotation of the head. Collectively, the orbiting rollers urge the fluid in a continuous flow through the aspiration line, at a generally steady and controllable flow rate, from the eye toward fluid-collection chamber.
A surgical apparatus which can be used to effect the above-described phacoemulsification procedure, is disclosed in U.S. Patent Application Publication No. 2006/0173404, which was published on Aug. 3, 2006.
It is well known that air is a highly compressible medium, and when the air bubbles generated during the operation of, the aspiration system are subjected to the vacuum pressure, the air bubbles expand under the vacuum pressure, and contract when the vacuum pressure is lowered. In addition, the air bubbles may coalesce, thereby forming large pockets of air within the aspiration system. In this manner, the presence of air within the aspiration system interferes with the efficient operation of the system, and could stall the operation thereof.
If a large volume of air is present in the system, it is feasible that the required vacuum pressure to sustain a delicate balance between the incoming flow rate of the irrigation fluid to the patient's eye, and the outgoing flow rate of the aspiration fluid and particles from the eye, could be undesirably altered, with catastrophic results to the patient's eye, and inefficient operation of the surgical procedure. Consequently, the minimization, if not the elimination, of air within the aspiration system is critically important.
In an effort to minimize the impact of air within the aspiration system, prior to the aspiration process, a purging of the aspiration line may, and should, be conducted to eliminate any air within the system. Notwithstanding the purging process, during the aspiration process, troublesome air bubbles may develop within the system, particularly in the cannula, the first aspiration tube, the filter housing, and the juncture connections of these components of the system.
One apparatus which considers the air-bubble concern is disclosed in U.S. Pat. No. 6,599,271 (the '271 patent”), which issued on Jul. 29, 2003, where an ophthalmic flow converter includes two flow paths, a first path for fluid flow and a second path for air flow.
As described in the '271 patent, the first path includes a first hydrophilic filter for filtering particles from an aspirated fluid, whereafter the filtered fluid is passed through a restrict opening of a manually-adjustable variable orifice, and then to a waste-storage cassette. Air, contained in the pre-filtered fluid of an aspiration line, is directed through a second hydrophilic filter in the second path, which bypasses the first filter and the variable orifice, and thereafter rejoins the filtered fluid.
As further described in the '271 patent, until the first filter becomes fully wetted by the incoming unfiltered fluid, air will pass through the first filter as well as the second filter. Thereafter, when the first filter becomes fully wetted, the first filter tends not to pass air, with the air then being directed through the second filter, to bypass the first filter.
In one embodiment of the ophthalmic flow converter described in the '271 patent, and illustrated in FIGS. 2 through 5 thereof, the converter is attached directly to an output end of an ultrasound needle within a hand piece, which is smaller in diameter than the converter. This difference in the diameters is necessitated by the design of a converter with two flow paths and two filters, and presents a potentially unwieldy combination for handling of the hand piece during an aspiration process.
In addition, the air which enters the first flow path prior to the first filter becoming fully wetted, may remain undesirably in the first path as the aspiration process continues. Further, even after the first filter becomes fully wetted, the first filter only tends not to pass air. Also, any air bubbles developed in the fluid subsequent to the fluid passing through the wetted filter, remain with the fluid and cannot be rerouted through the second filter.
Thus, there is a need for a surgical apparatus which, during a surgical procedure, will minimize, if not eliminate, the negative effects of air developed within an aspiration line of the surgical apparatus, during the flow of fluid in the aspiration line while operating in an aspiration mode.
In a phacoemulsification procedure, it is critical that a perfect fluid balance be maintained within the surgical apparatus wherein the flow rate of the aspiration fluid is always lower than the flow rate of the infused irrigation fluid, as noted above. If this balance is not maintained, a negative pressure may develop in the eye whereby the cornea and/or the entire eye will move and sometimes collapse. This condition can occur when a full occlusion blocks the opening of the free-end tip of, or occurs within, the hollow cannula, or elsewhere within the aspiration line, whereby the aspirated particle-laden fluid ceases to flow.
Typically, during normal operation of the surgical apparatus, a relatively low level of vacuum pressure, such as, for example, 20 mmHg to 50 mmHg, is developed by the peristaltic pump to facilitate the unoccluded suctioning of the particles, with the peristaltic pump is also simultaneously pumping the aspiration fluid to move the suctioned particles from the eye and farther into the aspiration line. If an occlusion occurs, for example, at the inlet opening of the free end tip of the cannula, the particle-laden fluid ceases to flow in the aspiration line, even though the peristaltic pump continues to operate. With the fluid ceasing to flow, and the pump continuing to operate, the vacuum pressure begins to increase.
During this period of occlusion, the vacuum pressure generated by the vacuum pump should be allowed to increase significantly, typically to 250 mmHg, or even higher to a range of 400 mmHg to 500 mmHg, in order to allow the increased vacuum pressure to quickly suction the occlusion into the hollow cannula, and farther into the aspiration line, and thereby allow the aspiration system to attempt to return to the perfect fluid balance. The presence of the increased vacuum pressure, when the occlusion breaks free, causes a potentially hazardous surge, or high flow rate, of the aspiration fluid within the aspiration line.
Such a surge of the aspiration fluid can lead to transient aspiration flow rates through the aspiration line that substantially exceed the flow rate of the irrigation fluid into the eye. This causes a sub-ambient pressure to be momentarily applied to surrounding tissue of the eye. The sub-ambient pressure condition may cause (1) an undesirable collapse of the anterior chamber of the eye, (2) undesirable damage to the posterior aspect of the lens capsule of the eye, and/or (3) undesirable movement of endothelium cells, which are critical to normal functions of the cornea, away from the cornea and towards the free-end tip of the cannula. On the other hand, independent of the formation of the above-noted occlusion, an irrigation-fluid flow rate, which is too high, may also move the endothelium cells away from the cornea, or undesirably cause the cells to be aspirated out of the eye.
The apparatus of the '271 patent includes the variable restrictive orifice, the restrictive opening of which is located in the sole path of flow of the fluid in the aspiration line thereof, during an aspiration mode as well as during a reflux mode. A manually-operable adjustment device is provided for selectively restricting the opening of the orifice, prior to the initiation of the phaco procedure, to limit the rate of flow of the fluid through the sole path of the aspiration line during an entire phaco procedure. The illustration of FIG. 5 of the '271 patent shows the opening of the orifice in a nearly closed position, which, as noted in the patent, is representative of the adjustment when the control device is being used. Further, after an air purging process, and before initiation of the phaco procedure, the desired flow rate for the phaco procedure may be obtained by using the manually-operable adjustment device to establish the desired size of the restrictive opening. This desired size of the restrictive opening remains unchanged during the entire phaco procedure in the aspiration mode.
The apparatus of the '271 patent is used to set the restrictive opening to a single size for the entire phaco procedure, and does not present any opportunity for adjusting the size of the restrictive opening during the procedure.
In U.S. Patent Application Publication No. 2002/0128560 (“the '560 publication”), which was published on Sep. 12, 2002, a fluid flow restrictor, having a fixed restriction passage is fixedly coupled to a filter housing to restrict the pressure drop within an aspiration system. The fluid flow restrictor of the '560 publication does not show any facility for adjusting the size of the restriction at any time during an aspiration procedure.
As disclosed in U.S. Pat. No. 5,106,367, which issued on Apr. 21, 1992, and companion U.S. Pat. No. 5,167,620, which issued on Dec. 1, 1992, an aspiration system includes a vacuum-controlled, tube-shaped resistor, having a fluid-flow passage, which is fixedly mounted in an aspiration line of the system to facilitate fluid flow therethrough. The resistor is composed of a material which will deform the fluid flow passage in response to an increase in negative pressure to reduce the cross-sectional area of the passage, and tends to reform to increase the flow area when the pressure of the aspiration line becomes less negative
Thus, there is a need for a surgical apparatus which, when operating in an aspiration mode during a surgical procedure, will respond dynamically to changing fluid-flow conditions within fluid-flow passage of an aspiration line of the apparatus and facilitate dynamic adjustment of the size of the fluid-flow passage to sustain an established fluid-flow rate within the aspiration line.
There is a further need for a surgical apparatus which, when operating in an aspiration mode during a surgical procedure, will respond dynamically to a surge of fluid flowing within a fluid-flow passage of an aspiration line of the apparatus and dynamically restrict the size of the fluid-flow passage to establish a desired fluid-flow rate and quickly suppress the surge to prevent potential deleterious effects therefrom.
If a stubborn occlusion is encountered, which will not break free upon the application of the above-noted high level of vacuum pressure, the surgeon can initiate a reflux procedure by controlling the aspiration system to reverse the operation of the peristaltic aspiration pump, provided that the surgical apparatus is capable of operating in a reflux mode. During the reflux procedure, the fluid in the aspiration line will flow in a reflux direction, i.e., toward the site of the surgery, whereby the occlusion is forced, within the aspiration line, in a direction toward the site of the surgery, to break free from the occluding position. It is important that, during the reflux procedure, the aspiration line be unrestricted, to insure that the flow rate of the aspiration fluid, in the reflux direction, is sufficient to force the occlusion free.
If an attempt is made with the apparatus of the '271 patent to operate the apparatus in a reflux mode, the pre-set restrictive opening will preclude the aspiration line from being unrestricted, and will prevent the development of a force sufficient to break free the occlusion. Even if the restricted opening is as fully open as possible, the restriction imposed by the fully-open restrictive opening will not facilitate the development of the force necessary to break free the occlusion.
In the '560 publication, and the '367 and '620 patents, there is no showing of any facility for allowing unrestricted fluid flow in a reflux direction during a reflux mode.
Thus, there is a need for a surgical apparatus which, during an aspiration mode of operation of a surgical procedure, will respond dynamically to a surge of fluid flowing within a fluid-flow passage of an aspiration line of the apparatus and dynamically restrict the size of the fluid-flow passage to establish a desired fluid-flow rate which will quickly suppress the surge to prevent potential deleterious effects therefrom, and where the surgical apparatus will provide an unrestricted fluid-flow passage within the aspiration line of the apparatus during a reflux mode of operation with a force sufficient to break free any occlusion in the aspiration line.